One altercation between police and protesters in which someone hurled a firework into a crowd has been caught on film.

Pictures and videos of protests are being posted on Twitter, where there is huge activity under the hashtag #AntonioMartin.

Some users have claimed that Martin was lying on the ground for a period of time - between 30 minutes and two hours - before emergency services arrived.

There is footage of Martin's mother, devastated at the news of his death, wrestling police to attend to his body. She was also filmed saying: "They started shooting. That's my baby."

Martin's mother told local news outlets that he had just left to visit his girlfriend, and said to NBC that she did not think Martin was armed.

There are, as well, users spreading misinformation.

One user, who spoke to The Huffington Post and was sourced by The Independent in an earlier version of this article, falsely claimed to be Martin's "best friend" and present at the time of his shooting.

The St Louis police will detail the incident at a press conference shortly.